Recently considerable progress in the genetic and molecular analyses of development has been obtained. There are powerful new molecular techniques which can be applied to analyze those genes important in the regulation of development, however those techniques must be used with genetically defined research animals. Isogenic lines are available in mouse and Drosophila, but are not available in the amphibian. The research presented in this proposal focuses on the development of clonal isogenic stocks of the amphibians, Xenopus laevis and Ambystoma mexicanum. The availability of such stocks would provide research materials of tremendous value to the biomedical research community.